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Respiratory infections linked to nearly 20-fold increased risk for myocardial infarction
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The risk for myocardial infarction is 17 times higher in the 7 days following a respiratory infection, according to research recently published in Internal Medicine Journal.
Researchers noted that though the chance of respiratory infections leading to myocardial infarction (MI) is low, primary care physicians should still consider informing their patients about ways to prevent some common infections.
“Much of the research linking respiratory infection to MI has been conducted using general practice records or regional registries without angiographic conrmation of [myocardial infarction],” Lorcan Ruane, BSc, MBBS, Sydney Medical School, New South Wales, Australia, and colleagues wrote. “The absence of angiographic data is an important limitation because elevated troponin and electrocardiogram changes may occur in the setting of respiratory infection and myocarditis without [myocardial infarction]. Previous studies have also tended to restrict their denition of respiratory infection to lower tract infections.”
To gather more data, researchers conducted interviews with 578 patients with angiographically confirmed MI within 4 days of their hospitalization, with the intent of assessing for recent exposure to respiratory infection symptoms and the usual annual frequency of these symptoms. The interview was based on a previous existing model and included questions related to possible acute triggers, including respiratory infection. The patients were asked about recent ‘flu-like illness with fever and sore throat,’ and gave a description of their symptoms and the start and end date of their symptoms. To eliminate potential bias, both the participant and interviewer were not told of the hypothesized hazard periods or potential modifiers for risk.
Ruane and colleagues then used case crossover methodology to compare exposure to respiratory infection prior to the onset of MI against the usual frequency of exposure in the past year.
They found that respiratory infection symptoms were reported by 100 (17%) patients within 7 days and 123 patients (21%) patients within 35 days before a MI. The relative risk (RR) for an MI within 1 to 7 days of a respiratory infection was 17 (95% CI, 13.2–21.8), and declined with subsequent time periods. For the patients who reported milder, upper respiratory tract infection symptoms, RR for MI occurring within 1 to 7 days was 13.5 (95% CI, 10.2–17.7). The risk declined with each subsequent 7-day period.
Researchers explained how physicians can put the study’s findings to use in their practices.
“Although patients should be reassured that the absolute risk that any one episode will trigger a heart attack is low, they need to be aware that a respiratory infection could lead to a coronary event, and should consider preventative strategies where possible, including flu vaccines, which in a 2015 meta-analysis were associated with a 29% reduction in heart attack rate,” Geoffrey H. Tofler, MD, department of cardiology, Royal North Shore Hospital, Sydney, told Healio Family Medicine. “Flu vaccines are underutilized, including in high risk individuals, so physicians should address patient misconceptions, including any concern that vaccine will result in influenza. While the vast majority of patients will settle with rest and adequate hydration, persisting or worsening symptoms need to be assessed by the physician, especially in high-risk individuals.”
“People should take measures to reduce exposure to infection, including flu and pneumonia vaccines where appropriate,” Thomas Buckley, PhD, department of cardiology, Royal North Shore Hospital, Sydney, said in a press release. – by Janel Miller
Disclosure: The researchers report no relevant financial disclosures.